Method for producing silicon steel strips having cube-on-face orientation



1964 SATORU TAGUCHI ETAL 3,

METHOD FOR PRODUCING SILICON smart STRIPS HAVING CUBE-ON-F'ACEORIENTATION F1196. July 9, 1962 3 Sheets-Sheet 1 FIG. I

Rotting direction The arrow shows the easy direction of magnetizationPIC-3.3

R0 i ing direction 8 Z) i i b INVENTORS Satoru Taguchi BY Ak/ra SakakuraTakashi Yasunari WMMIXM PM Dec. 29, SATORU TAGUCHI ETAL 3,153,564

METHOD FOR PRODUCING SILICON STEEL STRIPS HAVING CUBE-ON-FACEORIENTATION Filed July 9', 1962 3 Sheets-Sheet 2 L9 (gauss) L8 raxlo IAl6 0.9 l l l I oolo 0020 0030 0040 0050 0060 IN VEN TOR. Safo ru TaguchiAkira Sakakura BY Takashi Yasunari United States l atent C METHOD FGRPRUDUCKNG SILMIGN STEEL STRHS HAVING CUBE-GN-FAQE GREENTATEUN SaturnTagnchi, Airira Sakaitura, and Tahashi Yasunari, Yawata, Japan,assignors to Yawata iron and teei Co., Ltd, Tokyo, lapan Filed July 9,1962, Ser. No. 208,277 Claims priority, application Japan, Mar. 1%,1958, Gift/Z992; 9st. 8,1958, Eli/28,745

2 Claims. ((31. 148-411) This application is a continuation-in-partapplication of our co-pending applications Ser. No. 797,361, filed March5, 1959, and Ser. No. 844,450, filed October 5, 1959.

The present invention relates to a method for producing a so-calleddouble oriented magnetic silicon steel strip which has easymagnetization axes [001] in two rightangled directions in the rollingplane of the steel strip and in which a (001) plane appears in therolling plane.

Hitherto, silicon steel sheets (and this term is used hereinafter toinclude steel strips) have been used as a soft magnetic material, foriron cores of transformer, electric generators and the like. Manyattempts have been made 3,1635% Patented Eec. 29, 1964 2 process forproducing double oriented silicon steel having a desired thicknessgreater than that of the known doubleoriented sheets, which process canbe carried out successfully in a conventional industrial atmosphere.

An additional object of this invention is to provide a process forproducing double oriented silicon steel having excellent magneticcharacteristics, particularly in a comparatively high magnetic field,along two directions, a finally rolled direction and a transversedirection perpendicular thereto.

For a better understanding of the nature and objects of the invention,reference should be had to the following detailed description anddrawings, in which:

FIG. 1 shows the crystal orientations and easy magnetization directionsof crystal grains constituting single oriented silicon steel ([1) anddouble oriented silicon steel (b) and Wassermann type oriented siliconsteel (0).

FIG. 2 shows views of iron cores for transformers punched from singleoriented steel (a) and from double oriented steel (b).

FIG. 3 shows views of iron cores for rotors punched from single orientedsteel (a) and from double oriented to control the crystal orientationsof such silicon steel 7 sheets destined for the aforesaid uses in orderto obtain sheets of oriented silicon steel having a cubic crystalstructure, in which there exist 3 mutually-perpendicular directions ofeasy magnetization (directions of cube axes l00 and, which results inthe advantage that, when a magnetic field is applied parallel to any ofthese 10G directions, a minimum amount of energy is required tomagnetize the silicon steel.

The first type of oriented silicon steel that satisfied such requirementwas single-oriented silicon steel.

Single-oriented steel consists of cubes standing on edge, hence it isoften referred to as having cube-on-edge orientation which is of the(110) [001] type, as illustrated in FIG. 1(a) of the accompanyingdrawings. The arrow indicates that easy magnetization is possible onlyalong a single direction which is usually the direction of rolling. Infact, lines representing the other cube axis would extend out from thetop and the bottom of the sheet at angles of 45. Therefore, as is wellknown to those skilled in the art, the magnetic induction and othermagnetic properties are outstanding in the rollin direction, i.e., the[100] direction. However, in any other direction, for example, thedirection transverse to the rolling direction of the sheet, the magneticproperties are greatly inferior because of the magnetization is notparallel to the edge of the cubic crystal structure.

It has long been the desire of this art to produce doubleorientedsilicon steelsheets which have a cube-on-face orientation, i.e., (100)[001] type crystals as illustrated in FIG. 1(b) of the drawings. For ifsheets of a cube-onface or double orientedgrain texture can be produced,the easy direction of magnetization will be parallel to the length,width and heighth of the sheet; then the magnetic properties of thesheet would be outstanding both in the rolling direction of the sheetand in the transverse directions, i.e., the directions perpendicular tothe rolling directions and to each other, in the sheet;

An object of this invention is to provide a process for producing doubleoriented silicon steel consisting substantially of a cube-on-facecrystal, i.e., a (100) [001] type crystal and having consequentlyexcellent magnetic characteristics along the two transverse directions,from a hotrolled steel plate prepared by subjecting to a conventionalhot rolling a silicon steel body and which is produced by a conventionalmelting (steelmaking) method or casting method.

A further object of this invention is to provide a process for producingdouble oriented silicon steel by a heat-treat ment in a usual industrialatmosphere.

A still further object of this invention is to provide a steel (b).

FIG. 4 shows the reiation between the Al contents after hot rolling onthe one hand, and the magnetic characteristics after final annealing(the magnetic induction B and the iron loss W15/50 in the twooutstanding directions, i.e., the final rolling direction and thedirection perpendicular to it), on the other hand, as a result of aprocess mode A described hereinafter.

FIG. 5 shows the relation between the Al content after hot rolling andthe magnetic characteristics after final annealing (the magneticinduction B and the iron loss W15/50 in 2 directions, i.e., the finalrolling direction and the direction perpendicular to it), as a result ofa process mode B described hereinafter; six different hot rolled silicon steel materials (plate thickness: 2.0 mm.) having chemical analysesas indicated in Table l are cold rolled with a reduction of about 30% inthe same direction as that of hot rolling, then cold rolled with areduction of about 30% in a direction approximately at a right anglethereto, then annealed for a period of 5 hours at the maximum holdingtemperature at 1100 C., then again cold rolled with a reduction of inthe same direction as that of the second cold rolling, and thereafterfinally an nealed for a period of 15 hours at the temperature of 1150 C.

FIG. 6 is a graph with two curves showing the relationship between shorttime anneal temperature andcore loss after final anneal of the magneticmaterial produced according to mode A of the process according to ourinvention.

FIG. 7 is a graph showing the effects of the temperature of anintermediate box anneal over the magnetic properties of the magneticmaterial produced by mode A of the process according to this invention,and will be described in detail hereinafter.

FIG. 8 is a graph showing the relationship between the,

magnetic induction and thecold rolling reduction of the magneticmaterial manufactured by mode A of the proc-,

ess according to this invention, and will also be described in detailhereinafter. v

In FIGURES 48, a solid' line plotting black circle Q shows an iron lossin the final cold-rolling direction, a

solid line plotting circles 0 an iron loss in the direction areaseaveloped heretofore. It will also be clear from the drawings that, sincea double oriented silicon steel sheet has good magnetic properties intwo directions, i.e., the rolling direction and the directionperpendicular thereto, such a silicon steel sheet can be used to maketherefrom iron cores for electric machines far more advantageously thanit is possible when a conventional single-oriented silicon steel sheetis used. While, when punching an iron core for a transformer as shown inFIG. 2, the iron core must be made by combining four elements 1, 2, 3and 4 which are punched separately in the case of using asingle-oriented silicon steel sheet, the iron core can be made by only asingle punching, when double-oriented silicon steel sheet is used. Also,when an iron core for a rotor as shown in FIG. 3 is punched from asingle-oriented silicon steel sheet, the easy magnetization directiondoes not coincide with the direction of the magnetic field in the art ofthe teeth 7, which results in a reduced magnetic capacity of the rotor.On the other hand, the iron core punched from the double orientedsilicon steel sheet has good magnetizability at full capacity, andtherefore the weight of the iron core may be light.

For the above reasons, double-oriented silicon steel sheet offersconsiderable industrial advantages as compared With the conventionalsingle-oriented silicon steel sheet, but special metallurgical processesare needed in order to produce the desired double orientation becausethe cube-on-face, i.e., the (100)[001] orientation is not the usualconfiguration found in silicon steel.

For example, according to the method represented by German PatentAuslegeschrift 1,029,845, used by Vacuumschmelze Co., Germany,double-oriented silicon steel is produced by hot rolling a silicon steelingot obtained by vacuum melting, subjecting the hot rolled steel toseveral stages of cold rolling and repeated intermediate heat-treatmentsand, after final gauge has been attained, annealing finally in anoxygen-free inert atmosphere of high purity. However, this methodrequires many stages of cold rollings and intermediate heat-treatments,and it is also necessary that the atmosphere should be substantiallyfree from oxygen, moisture and other oxidizing agents, so that SiO(silica) will not be produced on the surface of the steel sheet duringthe annealing and, furthermore, in case S is formed, it can be reducedto Si during the annealing treatment. It is, however, extremelydifficult to maintain such annealing condition, at least on anindustrial scale. In addition, another important drawback of this knownmethod resides in the fact that crystal grains having ahnost complete(100)[001] orientation are grown when the thickness of the final productis less than 0.1 mm., but that, when the final product is thicker thanthe said limit value, the parallel relation between the rollingdirection and the [001] direction or between the direction perpendicularto the rolling direction and the [010] direction deterioratesconsiderably, and, therefore, crystal grains having complete (100)[00l]are no longer obtained, which makes it extremely disadvantageous as aprocess for producing iron core materials for heavy electric machines inwhich an article having a thickness of about 0.3 mm. is most desirable.

On the other hand, a process is also known in which an ingot having a(100) [001] orientation is made by casting molten silicon steel by usinga special apparatus and the ingot is hot-rolled, cold-rolled andheat-treated. However, it is difiicult to produce such an oriented ingotindustrially and even if such an oriented ingot is obtained, thiscreates ditficult problems in hot-rolling techniques, since the ingotmust not be reheated during hot rolling.

Under these circumstances, it will be clear that the production ofdouble-oriented silicon steel is very difficult to realize particularlyon an industrial scale. We have now succeeded in producingdouble-oriented silicon steel having excellent magnetic characteristicsin two directions, the rolling direction and the direction perpendicularthereto, by an industrial process for producing double-oriented siliconsteel which requires only the conventional industrial apparatus and nospecial, unusual operational methods. In the process according to ourinvention, a silicon steel element containing a small amount of Al ismade by a conventional steel making method, and the steel is subjectedto a conventional hot rolling to obtain a hotrolled sheet, which is thentreated with a novel mode of cold rollings including a cross rolling andheat-treatments in a conventional industrial atmosphere.

Moreover, in the known processes for producing doubleoriented siliconsteel sheets, considerably high cost is involved in carrying out theseconventional processes on an industrial scale, since the steel to beused must be of considerably high purity and must, therefore, beprepared in a vacuum melting furnace.

On the other hand, in the improved process of our invention, anyconventional steel melting method can be used, any specific measures arecompletely unnecessary in the necessary hot-rolling work, and theheat-treatment in the process according to this invention can be carriedout under conventional conditions without the necessity of providing anyspecifically prepared atmosphere.

Furthermore, since in the process according to the present invention,the crystal grain of [001] orientation being the constituent element ofthe produced double oriented silicon steel sheet grows independently ofthe thickness of the sheet, double oriented silicon steel having anythickness desired as electromagnetic materials can be produced.Therefore, the process of this invention represents a marked improvementover the known processes for producing double-oriented silicon steelsheets in which only articles having very limited thickness have beenproduced.

The objects of the present invention, as stated above, can be achievedby hot rolling a silicon steel element containing small but criticalamounts of Si and Al, and treating it by a process including a crosscold rolling and in this case, the process of this invention is based ona new phenomenon, namely that the crystal grain having a (100)[001]orientation grows only when the hot rolled sheet contains a criticalamount of Al and is cross-rolled and heat-treated.

A cross-rolling process had been described by Wassermann and by Bitter.However, the industrial value of this process is limited because theproduct obtained by their process shows a crystal orientation of theconstituent crystal grain of a (100)[011] type as shown in FIG. 1(0) ofthe drawings, and because, consequently, the easy magnetization axisappears in a direction at an angle of 45 with the rolling direction andin the direction perpendicular thereto.

In the process according to this invention, we have succeeded inproducing a double-oriented silicon steel sheet by subjecting ahot-rolled sheet containing critical amounts of Si and Al to across-rolling treatment, thereby growing a crystal grain having a (100)[001] orientation. Our inventive process which includes the aforesaidcross rolling treatment can be carried out in two different modes ofoperation which are designated as a process A and a process Brespectively hereinafter.

The silicon steel material (steel ingot) used as starting material inthis invention is preferably produced by a melting method and mustcontain above 2, and, to be really satisfactory, about 2.5% and up to 4%of Si and above 0.010 and indeed from 0.014% up to 0.040% of A1 whenusing process mode A, or above 0.010 to 0.050% and better, from 0.015 to0.041% of Al, when using process mode B (all percentages are by weight).Other allowable impurities may be contained in the starting materialjust as in conventional single oriented silicon steel and nounconventional restrictions need be imposed as to these impurities,except the aforesaid limits for Al and Si.

More particularly, the Si and Al contents of the steel, afterhot-rolling should be from 2.7 to 3.8% of Si and from 0.016 to 0.030% ofAl.

A typical, non-limitative analysis of steel suitably for use as startingmaterial in the process of the present invention, and yielding optionalresults is the following:

2.98 to 3.10% Si, 0.020% A1, 0.04% C, 0.10% Mn, 0.012% P, 0.015% S,0.10% Cu, 0.005% Ti and the bal ance Fe. g p l In regard to the carboncontent, carbon is not a limiting element in the composition of thematerial of the present invention. However, in the ordinary industriallyobtained ingot, it is diflicult to make the carbon content less than0.02% On the other hand, if the carbon content is more than 0.06%, itwill be very difficult in decarburization to eliminate the detrimentaleiiect of the residual carbon on the magnetic characteristics of theproduct. Therefore, a carbon content from 0.02 to 0.06% shall beadopted.

If the Si content is greater than 4%, the ingot becomes brittle when itis rolled, in particular, cold-rolled as will be stated later, whichcauses undesirable phenomena such as rupture and if the Si content isless than 2%, a ferriteaustenite transformation occurs during theannealing pros ess which will be explained later, whereby the crystalorientation, the production of which is the object of this invention,disappears. Also, in general, if the content "of Si is low, the electricresistance of the steel sheet is lowered, which results in increasingeddy-current loss and iron loss. Therefore, in this invention, thecontent of Si is limited to higher than 2.5 and up to 4%.

With regard to the content of Al, processes are known in which Al isadded in order to improve the magnetic properties of unoriented siliconsteel sheet. For example, in one known process, an aluminum-containingsilicon steel strip is produced by forming an Al-containing siliconsteel having a suitable, composition (Si 15%, Al 0.0l- 1.00% and C0.02%), rolling the steel into a steel strip and then annealing the.steel strip continuously at a tem- .perature of 1500 to 1750" F. in adecarburization atmosphere to reduce the content of C to lower than0.02%.

However, in this known process, Al is added, because it lowered whilethe temperature at which the silicon steel develops a 7 phase isapt tobe raised. This is said to have the practical efitectthat carbon, whichwould be dissolved in the steel, if Al were absent, remains out ofsolution, when Al is present, and in this state, C is available forremoval from the steel as carbon oxides gas.

However, such silicon steel of low watt loss values fails to show anoutstanding single or, two outstanding directions of permeability whichwould characterize oriented silicon steel.

silicon steel sheets has been disclosed as being of any advantage, andwhere, aluminum has been present in singl -oriented steel, it was merelyincidently, but since then, its presence was never provided forintentionally. in fact, the presence of Al in magnetizable steel hasusually been avoided as far as possible, since Al is apt to form oxidessuch as A1 0 and the like in steel, which are harmful to the magneticcharacteristics of the steel; and therefore, except for an unavoidablepresence of less than 0.01% Al, stemming from the starting materialsfrom which the steel is made, any content of Al has been, in general,eliminated. In double-oriented silicon steel sheet, no such effects aswere adscribed to the addition of Al in the case of non-oriented siliconsteel sheets, was generally expected, and, therefore, efforts wereusually made to maintain the Al content, if any, as low as possible.

Only very recently, Mobius has disclosed that steel 0 l which is to begiven (i00)[00l] cube texture, not by cross rolling treatment (90), butby an inclined-angle rolling to 70), must have, in the case of siliconiron alloys, a content of between 0.5 and 2.5% of Si, in the case ofaluminum iron alloys, a content between 0.5 and 2.0% A1, and, in thecase of silicon-aluminum iron alloys, the sum of the quantities ofsilicon and aluminum together should be between 0.5 and 2.5%.

in contrast thereto, it is a fundamental feature of the processaccording to our invention and indispensable for carrying out theprocess successfully that, after hot rolling, the silicon steel ingotused in our process has an Al content above 0.010 and up to 0.040%, whenused in process mode A, or up to 0.050% if used in mode B. The presenceof aluminum within the stated critical limits is desirable in theprocess according to this invention the advantages attained by theaddition of Al more than make up for the disadvantages. stated above,subject to certain conditions which will be explained I furtherhereinafter.

Aluminum can be present in silicon steel in two forms, namely asacid-insoluble Al and acid-soluble Al. The former consists mainly of A10 produced due to the strong aflini-ty of Al to oxygen and since it isharmful to the magnetic properties of steel, its formation must beavoided as much as possible, in this invention also. However, due to theprogress nrade in steel-making and melting techniques, it has becomepossible. to reduce greatly the content of acid-insoluble A1, even if alarge amount Another known process conceives .a treatmentof siliconsteel containing.1.9% of Si and 0.20% However, the purpose of adding Alin this known process is 1 to obtain a proper crystalline condition inproducing electric s-ilicon'stecl fiat stock, the last-mentionedprocess, without incurring the risk of intersecting the 7 loop in I thehigher carbon steels produced in the said known process.

The products of these known processes are thus concerned withnon-oriented silicon steel sheets and their magnetic properties areinferior to the double oriented Further 7 adding Al in the presentprocess has nothing to do with the purposes for which the same is addedin the abovedescribed processes. p I

Also, in the well known process for imparting to silicon steel sheet a(l10)[-001] texture,.generally referred to as Goes texture (see Patent1,965,559), no effect of an addition of Al as suggested in the case ofnon-oriented of Al'is added, by operating carefully during the addingprocess. We have found that, when the content of total Al is kept withinthe limits of 0.010 to: 0.050%, the content of acid-insoluble Alcontained init is in the order of 0.005% independently of the totalcontent,.provided that care is taken that a suflicient amount ofnitrogen is available in the atmosphere which is in contact with thesteel while the latter is being produced and prowssed. The remainingpart of Al, namely the acid-soluble Al is an important component of thisinvention and it consists of Al present in a solid solution in siliconsteel and Al which is present as a nitride such as AlN, of which theratio depends upon the contents of total Al in the silicon steel andthermal conditions, such as melting conditions, hot-rolling conditionsand annealing conditions, the reaction equation being as follows:

[Al] [N] @AlN I or electric furnace, N is present in the steel, and ifAl is also present in the steel, Al is deposited as AlN. On the otherhand, if specific melting apparatus, such as a vacuum melting furnaceand the like, are used, N is absent from the steel, and in this casehardly any AlN is formed even if a considerable amount of Al iscontained in the steel. In other words, unless such specific meltingapparatus is used in the production of steel ingot, but the latter isproduced by the common industrial techniques, and is hot-rolled, theacid-soluble A1 present in the hot rolled product consists partly ofAlN.

The AlN content should amount to at least 0.0029% and preferably atleast 0.0043 to 0.0045 and may be as high as 0.0073% and higher,calculated on the weight of the hot-rolled silicon steel.

In order to produce double oriented silicon steel by the processaccording to this invention, it is there-fore another indispensiblecondition that acid-soluble Al main- 1y consisting of AlN is presenteither in the hot-rolled steel sheet or, at the latest, in the steelsheet prior to cross cold-rolling. This can be achieved by castingsilicon steel material containing the above-defined small, but critical,amounts of Si and Al by any conventional steel-making method and/ormelting apparatus, which permits nitrogen to be present in the steel,i.e., either introduce the same, or maintain the same in solution in thesteel in sufiicient amounts that the major portion, preferably 60% andmore, of the aluminum present in the steel exists in acid-soluble formand a substantial portion of the latter as aluminum nitride, and thensubjecting it to a conventional hot-rolling. Therefore, this process isvery easy to carry out on an industrial scale and very economical ascompared with the melting method which has hitherto been used forproducing double oriented silicon steel sheets.

Wiener teaches in the United States i atent 2,965,526 a process forproducing a single-oriented silicon steel strip by cold-rolling andheat-treating a hot-rolled silicon steel containing in a range of 0.001to 0.05% at least one substance of a group consisting of metal sulfides,oxides and nitrides.

The diiferences between it and the present invention shall be describedmore particularly. First of all, the object product of said US. Patent2,965,526 is a singleoriented silicon steel sheet consisting of crystalgrains of such (110) [001] orientation as is shown in (a) in FIG- URE 1and shows favorable magnetic characteristics in the rolling directiononly, whereas that of the present invention is a double-oriented siliconsteel sheet consisting of crystal grains of such (100) [001] orientationas is shown in (b) in FIGURE 1 and shows favorable magneticcharacteristics in the two directions of the rolling direction and thedirection at right angles thereto. How industrially significant this is,is as already shown with examples in FIGURES 2 and 3. Secondly, thestarting material of said US Patent 2,965,526 is a hot-rolled siliconsteel containing about 2.2 to 5.25% Si, 0.001 to 0.05% of at least onesubstance of a group consisting of metal oxides, sulphides and nitridesand maximum of 0.02% C, the rest being iron, whereas that of the presentinvention is a hot-rolled silicon steel containing above 2.5 and up to4.0% Si, 0.010 to 0.050% Al, the larger part of which must exist asacid-soluble aluminum consisting to a substantial portion of AlN, apartfrom the unavoidably present small amount of acid-insoluble aluminum,and carbon in the range of 0.02 to 0.06% and is evidently a materialquite different from the above. Thirdly, the treating process of the US.Patent 2,965,526 is the two-step cold-rolling method developed by N. P.Goss, whereas that of the present invention is a two-step or three-stepcold-rolling method including cross-rolling and is quite different fromthe above.

The two above-mentioned modes A and B of carrying out the processaccording to the invention in practice will now be described in detail.

PROCESS MODE A Hot-rolled sheets, preferably in the form of strips of1.6 mm. in thickness obtained by subjecting to a conventional hotrolling ingots containing the above-defined critical contents of Si andAl, that are produced by a conventional electric furnace steel-makingprocess, permitting formation of aluminum nitride as described above,are used as starting material.

More particularly, FIG. 4 gives the curves showing the relationshipbetween the aluminum content prior to final anneal, core loss afterfinal anneal, and magnetic induction radius when various specimens ofthe aforesaid start-. ing material designated as A, B, C, D and E withthe composition shown in Table 1 below or similar compositions includingvarying contents of aluminum and silicon within the above-defined limitsare subjected to hot rolling to a thickness of 1.6 mm., pickling toremove scale resulting therefrom, an initial cold rolling in onedirection with a reduction of 60%, then a final cold rolling in adirection approximately at right angle thereto with a reduction of thena short time anneal for about four minutes at the temperature of 800 C.,and lastly a final anneal for fifteen hours at the temperature of 1150C.

Table 1 ANALYSIS OF STEEL AND MAGNETIC PROPERTIES Magnetic Test(Epstein) Analysis, percent Gore Loss Magnetic Specimen Industion C SiAl in all Acid-sol- N in all N as AlN Wio so W15/5U Bio uble Al Remarks:

1. WlO/bfl watts X 10 kilogausses at a frequency of 50 c.p.s.

Unit: watts per kilogram; Wis/an Watts 15 kilogausses at a frequency of50 c.p.s. Unit: watts per kilogram.

2. B10 magnetic induction at 10 ocrsteds.

Unit: Gauss.

3. Referring to Magnetic Test Value (Epstein), upper valucreicrs to thatof final rolling direction while the lower that of the direction rightangle thereto.

to each other hereinafter.

Magnetic valuc'is obtained from two directions at right angles 4.Referring to analysis of specimens, upper analysis refers to that of hotrolled silicon steel stock while the lower to that of prior to finalanneal.

.5. Each specimen consists of the above composition and the balance,iron and incidental impurities, de-

scribed hereinbciore.

It will be easily understood from the analytical data for hot-rolledsheets, which are identical with those for the sheets prior to the finalanneal, in Table 1, that the content of acid-insoluble Al is almostconstant, i.e., in the order of 0.005%, ind'ependently'of the totalamount of Al. It will also be easily understood that the amount ofacid-soluble Al changes in proportion to the amount of total Al so thatmore than 60% of the total amount of aluminum present exists asacid-soluble Al and a substantial portion of the latter as AlN. In otherwords, in the case of using no special melting apparatus which removesnitrogen from the treated steel, the acid-soluble Al in the producedhot-rolled sheets consists to a substantial portion, preferablyone-third, of AlN.

Referring again to Table 1 and FIGURE 4, While in the case. or" startingmaterials A and E, the magnetic properties after final anneal areordinary, forexarnple, the magnetic induction B is less than 17,000gausses in each product, in the case of the starting materials B, C andD, the magnetic induction B in each product is about 18,000 gausses inboth outstanding directions, namely the direction of final rolling andthe direction perpendicular thereto, and the products thus show theoutstanding properties of double oriented silicon steel.

The values (Epstein'test) of magnetic induction B in the rollingdirection of top-class products by three steel manufacturers which havebeen marketed heretofore as single oriented silicon steel are as followsby the catalogs of the manufacturers:

As the value of B is a value of a magnetic induction in a magnetic fieldof 10 oerstcds, the higher this value is, the better the parallelrelation between the easy magnetization axis, i.e., the [100] axis andthe rolling direction. The value of B in an oriented silicon steel sheetis usually higher than 17,000 gausses. Since, moreover, in singleoriented silicon steel, an easy magnetization axis does not appear inthe direction perpendicular to the rolling direction as shown in FIG.1(a), the value of B in the said transverse direction is far lower. Onthe other hand, in the products of this invention obtained from thestarting materials A, C and D, the values are about 18,000 gausses inboth directions, which proves that the product in this invention isclearly double-oriented silicon steel of the type illustrated in FIG.1(1)). Thus, we have found by comparing and investigating the relationsbetween Al contents after hot rolling and magnetic inductions ofproducts, that, contrary to the teaching of the most recent knownprocess (US. Patent 3,008,856), the

Al content after hot rolling must be restricted to the range between0.010 and 0.040% in the case of the treatment by the aforesaid processmode A. In particular, when the Al content is in a range of 0.015 to0.030%, the magnetic induction B of the final product is higher than18,000 gausses in the direction of the final rolling, as Well as in thedirection perpendicular thereto, which values are even better than thebest values of magnetic induction B of a conventional single. orientedsilicon steel in the rolling direction.

The thickness or gauge of the hot rolled steel is an importantrequirement for the production of a doubly oriented silicon steel sheetor strip. In our process mode A, the thickness or gauge of the startingmaterial should be preferably 2.5 to 10 times of the desired finalthickness On the other hand, if the guage of the hot rolled siliconsteel is too thick, the final gauge of the product will be too thickafter the predetermined cold rollingreduct-ion, which results in anincrease of eddy loss.

In view of the above requirements, the gauge of the hot rolled siliconsteel is preferred to be from 1 mm. to 4 mm. Particularly, about 1.6 mm.is most preferred, which is about three to five. times the final gauge,taking both the final and the necessary cold rolling into account.

The hot rolled silicon steel with a predetermined gauge is subjected toa pickling step, and then to cold rolling.

The reduction in thickness by cold rolling is of the greatest importantin view of the combination of two cold rolling directions. In oneembodiment of theinvention, the overall reduction is preferred tobewithin the range of 60% to 90%. The embodiment which comprises'coldrolling the steel in one direction first with a reduction of 40% toagain cold rolling it in another direction at light angle thereto, witha reduction of 30% to 70%, and finally annealing the thus cold rolledsteel, has resulted in the desired cube oriented silicon steel sheet orstrip we have in view.

It .is most preferred to take the combination of twocold rolling stepsconsisting of the initial cold rolling in one direction with a reductionof about 60% and the final cold rolling in a crosswise direction thereto(at an angleof about with a reduction of about 50%.: When the directionof the initial cold rolling step coincides with or deviates at a certainangle from that of hot rolling the starting material, we have found thatthe iron core loss and magnetic induction determined after the finalanneal in reference to the one direction of initial cold rolling are notappreciably different from those obtained from the other direction offinal cold rolling. It is important, in order to obtain good results inthe process of the invention, that'the two directions of cold rollingare approximately at right angles to each other. The more the angledeviates from the right angle, the more difiicult will it be to obtain aproduct favored with two axes of easy magnetization [001]. In view ofthe above consideration, we have discovered that a permissible anglecrossing to each other should deviate less than and, to obtain goodresults, not more than :15", from the direction of the right angle. I

In a commercial production embodying the process of our invention, thehot rolled silicon steel containing more than 2.5 and up to 4% ofsilicon and between 0.010% and 0.040% aluminum is cold rolled in onedirection, then sheared off to a sheet of length, and

again cold rolled in the other direction at right angle i15 thereto inthe form of sheet. Alternatively, another silicon steel strip isproduced by welding sheared sheets end to end together in such mannerthat the longitudinal direction of the strip makes a direction at rightangle, or deviating by less than 15 therefrom on either side, to thedirection of initial cold rolling, whereupon the strip is again coldrolled continuously.

The welding operation of sheets to strip makes no difference for theadvantage of the invention, even though it may be carried out at anystep after the initial cold rollingprocedure.

A preferred commercial production carrying out the process of theinvention with the hot rolled silicon steel strip as starting materialcomprises the following steps:

A hot rolled silicon steel strip having a predetermined thickness ispickled to remove scale resulting from hot rolling with theabove-defined definite reduction to produce cold rolled silicon strip.The cold rolled silicon strip is sheared off to a number of sheets ofdesired length. Subsequently, a new silicon steel strip is produced byWelding the sheared length of sheets end to end together in such amanner that the longitudinal direction of the new strip forms adirection at right angle or deviating less than 15 therefrom, to thedirection initial cold rolling, then the thus produced strip is againcold rolled continuously with a predetermined reduction. Alternatively,

a sheared length of sheet is again cold rolled sheet by sheet in adirection at right angle or deviating less than :15" from the directionof initial cold rolling, with a predetermined reduction, then a numberof twice coldrolled sheets are welded end to end together to produce anew cold rolled strip. Of course, the above-described subsequenttreatment will be given to the cold-rolled strip thus obtained.

The temperature of the short time anneal to be imparted to the siliconsteel sheet or strip which has been cold rolled to the final gauge hasan influential effect on the primary recrystallization structureresulting from the anneal, and the secondary recrystallization of theseed crystal grain having a (100) [001] type orientation will dependupon the primary recrystallization structure.

FIGURE "6 shows the influence of the annealing temperature on the ironcore loss after the final anneal of a product which has been obtained bythe process of the invention wherein a hot-rolled silicon steelcontaining 0.03% carbon, 3.02% silicon, 0.018% aluminum in all, and0.013% acid-soluble aluminum with a gauge of 1.75 mm. was firstcold-rolled in one direction with a reduction of 60%, and then againcold rolled to final gauge in another direction approximately at rightangles to the direction of the first cold rolling, with a reduction of50% and then annealed for four minutes at a temperature ranging between700 and 1,200 C. It is clear from FIG- URE 6 that the temperature atwhich a short time anneal should be carried out is preferably atemperature between 750 and 1,000 C., in order to obtain a producthaving good magnetic properties, while at a higher temperature than theabove upper limit, even for a short period of time only, the graingrowth of primary recrystallization structure may become so considerablethat selective secondary recrystallization in the final anneal will beprevented, although the advantage of the present invention may not beentirely lost. Further, it is to be understood that the advantage of theinvention will not be lost as long as the temperature of the short timeanneal is Within the range between less than 750 C. and higher than therecrystallization temperature. However, the temperature ranging between750 and 1,000 C. specified herein above is preferred for production onan industrial scale, since the lower temperature takes a longer, andtherefore uneconomical, time towards attaining the completelyrecrystallized structure. The time required for anneal at the abovetemperature range takes usually about one minute for the cold rolledstructure of the steel to be converted into the recrystallizedstructure. Since the silicon steel stock contains approximately 0.04%carbon, decarburization is required at the same time to an extent atwhich crystal growth may not be interfered with by the presence ofcarbon in the final anneal. We have discovered that a maximum of up tofour minutes is required for continuous anneal in view of the thicknessof the material and other requirements. It is to be understood, however,that the period of time for the short time anneal should not limit thepresent invention. This anneal is carried out usually in a neutral orreducing atmosphere, but is not necessarily limited thereto. Further, itis considered that the temperature ranging between 750 and 1,000 C.specified above is beneficial to commercial production because adecarburizing reaction is most actively going on at the abovetemperature in the presence of a small amount of moisture. A siliconsteel sheet or strip which has been annealed for a short period of timemay be subjected to pickling depending on its surface conditions.

Referring to the last anneal, an anneal at a temperature above 900 C. inthe reducing atmosphere for a period of time more than at least fivehours is required in order to produce a cube-oriented silicon steelstrip having low core loss and high magnetic induction values. Thecomplete secondary recrystallization may not be developed by an annealat either lower temperature or shorter time than that defined above. Apractical temperature available for the commercial production of theinvention is preferred to be between 900 and 1,300 C., since an annealat either a temperature above l,300 C. or for a time longer than fortyhours is not so effective. Annealing at a temperature outside the rangedescribed above, however, will not lose the fundamental advantage of ourinvention.

By the improved process according to the invention, it becomes possible,for the first time, to obtain uniform results of double orientationsteel made with conventional apparatus available in industry.

PROCESS MODE B In the following Table 2 there are compiled data obtainedby applying above-mentioned mode B of carrying out the process of theinvention to hot-rolled sheets or strips of 2 mm. thickness, which areproduced by subjecting to a conventional hot-rolling process the ingotsproduced, in turn, by a conventional open-hearth steel-making process;the hot-rolled ingots are cold-rolled to a direction which is identicalwith the hot-rolling direction, at a reduction rate of about 30%, thencold-rolled in the direction perpendicular to the first cold-rollingdirection at a reduction rate of approximately 30%, thereafter annealedfor 5 hours at a maximum temperature maintained at 1100 C., cold-rolledagain at a reduction rate of in a direction coincident with thelast-preceding rolling direction in the aforesaid cross rolling, andthen finally annealed for 15 hours at 1150 C.

In FIG. 5 there are shown the relations between the Al contents in thehot-rolled sheets and the iron loss values and magnetic induction valuesof the final-annealed sheets.

Table 2 ANALYSIS OF STEEL AND MAGNETIC PROPERTY Mag. test (Epstein)Analysis (Percent) Iron loss Magnetic Sample Induction C Si Total AlAciil-lsol. Total N N as AIN W15/50 1310 A 0. 04 3. 05 0.005 0. 0020.0035 0. 0005 1. 15, 200 1. 87 15, 250 B" 0. 04 3.01 0.015 0.010 0.0045 0.0029 1. 42 17,150 1. 40 17, 400 C 0. 04 3. 11 0. 021 0.016 0.0049 0. 0045 1. 04 18,050 1. 09 17, 950 D 0. 04 3.02 0.026 0.020 0. 00600. 0059 0.99 18, 250 1.01 18,150 E 0. 04 3.06 0. 041 0. 032 0.0078 0.0073 1. 19 17,800 1. 26 17, 700 F 0. 04 3.01 0. 065 0.051 0. 0080 0.0070 1. 47 17, 1. 55 17,000

Notes:

1. W means an iron core loss at 15,000 gausses measured per frequency of50, and its unit is wJkg.

2. B means a magnetic induction at 10 oersteds, and its unit is gauss.

3. In reference to the magnetic property, the upper one is the valuemeasured along the final rolling diree tion and the lower is that alongthe direction at a right angle thereto.

As clearly indicated in Table 2, good orientations. in twodirections ofcold rolling and a low core loss are given to the hot rolled siliconsteel material after the final anneal while, on the contrary, similarresults are not obtained by the conventional silicon steel containingeither less than 0.010% Al or more than 0.050% A1 despite of the sametreatment.

From the analytical data after hot rolling shown in Table 2, it can beseen that the amount of acid-insoluble Al remains almost constantindependently of the total amount of A1, and acid-soluble A1 mainlyconsists of AlN, which data are very similar to the analytical dataafter hot rolling stated in process A, supra.

Referring now to Table 2 and FIGURE 5 more in detail, while. in the caseof starting material A, the magnetic properties after final anneal arelow, for example, the magnetic induction B is less than 17,000 gausses,in the case of the products obtained starting materials B, C, D, E andF, the magnetic induction B of each product is about 18,000 gausses inthe two outstanding directions, i.e., the direction of final rolling andthe direction perpendicular thereto, which shows that the products areindeed, improved double-oriented silicon steels. have found that theycontent of Al must be limited to the range between 0.010 and 0.050% inthe case of the treatment by process mode B. We have further found that,while even in the case of material F containing 0.065% of Al, themagnetic induction B of the final product is higher than 17,000 gausses,yet, as the content of Al is more. than 0.050%, the amount ofacid-insoluble Al increases, as already stated, which influences theiron loss and other magnetic properties in an undesirable manner.Therefore, the Al content is in a range of 0.020 to 0.035%, the magneticinduction B of the final product is higher than 18,000 gausses in thedirection of final rolling and the direction perpendicular thereto,which is an excellent increase above the value of magnetic induction Bwhich a conventional single-oriented silicon steel shows in the rolling.direction.

' Now, each of the processing steps for carrying out the mode B of theprocess according to the invention will be described. As has beenmentioned before, the gauge or thickness of hot rolled steel is animportant factor in order to manufacture a double-oriented silicon steelsheet or strip we have in view. In the case of mode B, the gauge of thehot-rolled silicon steel starting material should be preferably 5 to 30times as thick as the final desired gauge. This gauge is closely relatedtothe total reduction of cold rolling described hereinbelow, anexcessiveiy thin gauge of the hot-rolled material leading to the samediificulties as described under Process mode A, and, conversely, anextremely thick gauge thereof resulting in a thick gauge of the finalproduct obtained by the reduction required for cold rolling, will alsoresult in an undesirable increase of eddy current loss due to, the thickgauge.

Accordingly, the gauge of the starting material is usually preferred to,be from 0.7 to 13 mm., and particu larly, about 3 mm. gauge of thestarting material is desired taking both the final gauge and thenecessary cold rolling reduction into account.

The hot rolled silicon steel is pickled in the usual mannor in order toremove scale resulting from hot rolling. The reduction in thickness bycold rolling carried out after pickling in two stages in directions atright angle to each other is of utmost importance depending on thecombination of rolling directions. In this mode B, an overall reductionof 44-80% is preferred: the primary c old rolling reduction in onedirection should be 3060*%, and the seoondary cold rolling reduction inthe other direction at a right angle thereto. -50%. When the mostdesirable gauge, 3 mm., of the above hot rolled steel is adopted, thecombination of a cold rolling reduction of 40% in one direction and asecond reduction of 40 in the other direction at right angle thereto ispreferable.

Two types of the final product are obtained by the process of thisinvention: one is obtained by the process which involves a direction ofprimary cold rolling coinciding with that of the preceding hot rolling,and the other is obtained by the process which involves a direction ofprimary cold rolling being at a certain angle to that of hot rolling.When these two products are compared, hardly any appreciable differenceis perceived between iron core losses and magnetic inductions determinedalong the two directions, respectively, after the final anneal. However,considerable attention should be paid to the fact that the degree of anangle at which the secondary cold rolling is carried out relative to thedirection of the primary cold rolling has a significant influence on themagnetic properties of the product after the finalanneal. In accordancewith the present invention, approximately is the most preferred anglebetween the primary and secondary rolling directions. The more thisangle deviates, the more difiicult is it to develop the axis of easymagnetization [001] in the two directions. We have found that thedesired doubly-oriented silicon steel sheet or strip. could not beobtained, if the deviation from the right angle amounts to 15 or more.Therefore, the permissible degree of deviation of the crossing anglefrom 90 is within the range of :15" in mode B as well as in mode A ofcarrying out the process of our invention.

We employ, for instance, a hot rolled steel strip as silicon steelstarting material. When this steel material in strip form is subjected.to the required process of the invention, the silicon steel strip havinga predetermined gauge is first pickled toremove hot rolling scale, thencold rolled with the necessary reduction to obtain a cold rolled steelstrip, which is cutinto a number of sheets of a predetermined length,two or more sheets are welded together end to end in order to make a newsteel strip the longitudinal direction of which is in a direction at anangle of approximately 90 (with a deviation within the range of :15) tothe direction of the primary cold rolling, whereupon the welded strip issubjected to the secondary cold rolling, further followed by thesubsequent treatment described further below.

In case of a steel strip as a starting material in this invention, thereare several processing methods to bev considered as follows:

(1) A first cold rolling is applied to the steel in the form of a strip,and the subsequent processing steps are applied to it in the form of asheet;

(2) A first cold rolling is applied to a steel strip which is then cutinto a number of sheets of a predetermined length, then a second coldrolling is applied to the steel in the form of a sheet in a direction atan angle of 90 (with a deviationwithin the range of :15 to the direction of the first cold rolling, then two or more of such twice coldrolled sheets are welded together end to end to form a new strip whoselongitudinal direction is equal to either one of the two directions ofcold rolling, and thereafter the subsequent processing steps describedfurther below are applied to this new strip;

(3) A first cold rolling is applied to a steel strip, which is then cutinto a number of sheets of predetermined length, then a second coldrolling and an intermediate box anneal. (described hereinafter) areapplied to the steel in the form of a sheet under the requiredconditions, then two. or more sheets are welded together end to end toform a new strip whose longitudinal direction is equal to either of thetwo directions of cold rolling, and thereafter the subsequent processingsteps are applied to the new strip; and

(4) A first cold rolling is applied to the steel in the form of a strip,which is then cut into a number of sheets of predetermined length, thena second cold rolling, an intermediate box anneal and a final coldrolling, described further below, are applied to the steel in the formof a sheet under the required conditions, then two or more 15 sheets arewelded end to end together to form a new strip whose longitudinaldirection is equal to either of the two directions of cold rolling, andthereafter the subsequent processing steps are applied to this newstrip.

When a hot-rolled steel sheet is used as starting material, there arealso several processing methods to be considered as follows:

(1) A first cold rolling is applied to a steel sheet in one direction,then this steel sheet is cut into sheets of a predetermined length, thentwo or more sheets of this length are welded together end to end to forma new steel strip whose longitudinal direction is at an angle of 90(with a deviation within the range of :15") to the direction of thefirst cold rolling, and thereafter the second cold rolling andsubsequent processing steps are applied to this new steel strip;

(2) Two cold rolling steps in two crossing directions are applied to thesteel in the form of a sheet, then two such sheets are welded togetherend to end to form a new strip whose longitudinal direction is the sameas either of the two crossing directions, and thereafter the subsequentprocessing steps are applied to this new strip;

(3) Two cold rolling steps in two directions and an intermediate boxanneal (described hereinafter) are applied to a sheet, then two or moreof such sheets are welded together end to end into a new strip whoselongitudinal direction coincides with one of the two crossingdirections, and thereafter the subsequent processing steps are appliedto this new strip; and

(4) A series of the required steps up to the final cold rolling(described further below) is applied to the steel in the form of asheet, then two or more sheets are welded end to end together to form asteel strip, and thereafter the subsequent processing steps are appliedto this strip. It is to be understood that the above described weldingoperation is not always necessary.

An intermediate box anneal imparted to the silicon steel sheet or stripreduced in thickness to an intermediate gauge by two cold rolling stepsin two mutually crossing directions has an important influence on therecrystallized structure to be produced by subsequent annealing. In thisinvention, the maximum holding temperature range should be preferablyfrom 850 to 1200 C. during the intermediate box anneal.

FIG. 7 is a graph showing the effect of the temperature of theintermediate box anneal on the magnetic properties of a magneticmaterial produced by the process of this invention, wherein a hot rolledsilicon steel containing 3.02% Si, and 0.026% Al was subjected to afirst cold rolling with a reduction of about 30% in the same directionas that of hot rolling, then again to a second cold rolling with areduction of about 30% in a direction approximately at right anglesthereto, then to anneal for a period of 5 hours at a temperature if 800to 1200 C. as the maximum holding temperature, then again to a finalcold rolling with a reduction of 70% in the same direction as that ofthe second cold rolling, and lastly to a final anneal for a period of 15hours at a temperature of 1150 C.

It is clear from FIG. 7 that the higher the maximum holding temperature,the more effective the anneal, but FIG. 7 also shows that this effectchanges very little at temperatures above 1000 C. However, the magneticproperties will decrease at temperatures below 850 C. Accordingly, froma commercial point of view, we prefer the maximum holding temperaturerange for the intermediate box anneal to be 850 to 1200 C. An atmosphereof either neutral or reducing gas medium is usually employed, but we donot limit the process of our invention thereto. Sufiicient nitrogenshould, of course, be present in this medium.

The reduction in thickness of the final cold rolling procedure is animportant factor for attaining the doubleoriented silicon steel we havein view, and the direction at which this final cold rolling is carriedout should be a direction approximately equal to either of two crosswisedirections of the preceding two cold rolling stages. From a commercialpoint of view, the selection of the same direction as that of the secondcold rolling is most practical.

FIG. 8 is a graph showing the relationship between the magneticinduction and the cold rolling reduction of a magnetic materialmanufactured by the process of the invention wherein a hot rolledsilicon steel material of 3.0 mm. thickness and containing 3.05% Si and0.034% Al was subjected to a first cold rolling, with a reduction of40%, in the same direction as that of hot rolling, then again to asecond cold rolling in a direction approximately at right angle theretowith a reduction of 40%, then to an anneal for a period of 5 hours at atemperature of 1100 C., the maximum holding temperature, then to a finalcold rolling in the same direction as that of the second cold rollingwith a reduction ranging from 19 to 84%, and lastly to a final annealfor a period of 15 hours at a temperature of 1150 C. The foregoingresults show that the reduction in thickness by the third or final coldrolling procedure is preferably within the range of 50 to 84%, and moreparticularly, a reduction of approximately 70% is most desirable.

As mentioned above, the silicon steel sheet reduced in thickness to thefinal gauge by the foregoing processing steps is subjected to a finalanneal. With a view to attaining a double-oriented silicon steel striphaving a low iron core loss, it is required to anneal the steel for aperiod of more than 5 hours at the maximum holding temperature of above1000 C. in a neutral or reducing atmosphere. By an anneal at a lowertemperature than the above, a complete growth of crystal cannot bedeveloped. Conversely, an anneal either at an elevated temperature ofabove 1300 C. or for an extended period of more than 40 hours will notdevelop the desired effect in a satisfactory manner despite of theelevated temperature or the extended anneal time. Accordingly, we prefera temperature range of 1000" to 1300 C. as the best commerciallyeffective anneal. However, the fundamental effect of the presentinvention will not be lost completely by an anneal deviating from therange of either temperature or period of time mentioned above.

The desired double oriented silicon steel sheet or strip can bemanufactured in accordance with the complete process of this inventiondescribed hereinabove. It is to be understood that the carbon content ofthe product after the final anneal should be the least possible, andmore particularly, a content of less than 0.005% C is most desirable.

Silicon steel used as starting material in carrying out the process ofinvention may usually contain 0.020.06% C. Therefore, a decarburizinganneal should be effected in order to reduce the carbon content,provided that it has not been reduced as desired by the intermediate andfinal box anneals. To this end, various known processes of anneal may beapplied in practicing our invention, and We do not intend to limitourselves to a particular one. For example, decarburization can beachieved by a process which comprises subjecting a hot rolled materialwith scale thereon to a box anneal, and also by a process whichcomprises subjecting a steel material either after two cross coldrolling steps or after the final cold rolling step to a short timeanneal in an atmosphere containing either neutral or reducing gas and asmall amount of moisture. We have discovered that the carbon content ofthe final product can be easily reduced to less than 0.0 05 by means ofeither of the above two processes of decarburization or by bothcombined.

We therefore, recommend that a box anneal with scale at a temperature of650-900 C., and a short time anneal in an atmosphere containing a littlemoisture at a temperature at 750-950 C. be effected in the process ofour invention.

At first glance, it may seem that the number of steps in the processmode B is, as stated above, more than that of l 7 the process mode A andconsequently that the process mode B is not as economical as the processmode A. However, as the permissible range of Al content for impartingthe magnetic properties of double oriented silicon steel (according to acommonly applied standard B of the silicon steel must be higher than17,000 gausses in a rolling direction and a direction perpendicularthereto), is broader in process mode B, the latter is less subjected tothe troubles which may be caused by the segregation of Al in thematerial. Also, the magnetic properties of the product obtained from amaterial containing the most suitable amount of Al by the process mode Bare somewhat better than'those of the product obtained by the processmode A.

, Our invention is further illustrated but not limited by the followingexamples:

Example 1 Hot rolled silicon steel stock containing 0.04% C, 2.98% Si, atotal content of 0.019% Al, comprising 0.015% acid-soluble Al and 0.0061of AlN, and having a thickness of 1.6 mm., was pickled, cold rolled witha reduc tion of 60% in one direction, then again cold rolled with areduction of 50% in another direction approximately at right anglethereto to a final gauge of about 0.33 mm. thickness. The thus treatedsilicon steel was subjected to a continuous anneal for four minutes atthe temperature of 800 C. in order to decarburize and recrystallize it,and to a final box anneal for hours at the temperature of 1150 C., todevelop the magnetic properties thereof. Magnetic tests according toEpstein were conducted on a sample taken from the above material withregard to the direction of the final cold rolling and also the directionat right angle thereto after the stress relief anneal, the results ofwhich test are shown in the respective columns of Sample C of Table 1 asmagnetic induction and iron core loss. As illustrated in FIG. 9, themagnetic torque curve diagram of this product shows that it is favoredwith an excellent structure of cube orientation.

Example 2 Hot rolled silicon steel strip containing 0.04% C, 2.99% Si, atotal content of 0.023% A1 comprising 0.018% acid-soluble Al and 0.006l%AlN, and having a thickness of 1.6 mm., was pickled, cold rolled with areduction of 60% in the same direction as that of the preceding hotrolling to produce a cold rolled silicon steel strip of 0.64 mm.thickness. Subsequently, the silicon steel strip was sheared off to anumber of sheet of definite length, which were Welded together sheet bysheet in order to produce a new silicon steel strip Whose longitudinaldirection was approximately at'right angle to the direction of theinitial cold rolling. The new silicon steel strip was again cold rolledwith a reduction of about 50% to a thickness of 0.33 mm. The cold rolledstrip was subjected to a continuou anneal for four minutes at atemperature of 800 C. followed by a box anneal for 15 houre at atemperature of l l50 C. Magnetic tests were conducted on an Epstein testsample taken from the above magnetic material with regard to itslongitudinal direction and also to the direction approximately at rightangle thereto, after the stress relief anneal, the results of whichtests are shown in the respective column of Sample D of Table 1 asmagnetic induction and iron core loss.

Example 3 A hot rolled silicon steel material of 2 mm. thickness,containing 0.04% C, 3.06% Si and 0.030% A1 (comprising 0.024% ofacid-soluble Al, and 0.0069% of AlN) is cold rolled with reduction of30% in one direction, then again cold rolled with a reduction of 30% inanother direction displaced approximately at a right angle to the firstrolling direction to an intermediate gauge of 0.98 mm., and annealed fora period of 10 hours at the maximum holding temperature of 950 C.

Thereafter, this steel is further cold rolled with a reduction of 68% inthe same direction as that of the second cold rolling step describedabove to a final gauge of 0.31 mm; and then finally box-annealed for aperiod of 20 hours at a maximum holding temperature of 1200 C. todevelop the magnetic properties thereof.

From this product, Epstein samples are taken alongthe final rollingdirection and also along the direction displaced at a right anglethereto, respectively, and magnetic tests are conducted on them afterthe stress relieving anneal, the results of which are as follows:

io (s (iv-I e) Final Rolling Direction 17, 800 Right Angle DirectionExample 4 The same hot rolled silicon steel material as in Example 3with scale thereon is box-annealed for a period of 5 hours at atemperature of 680 C., then cold rolled with a reduction of 30% in onedirection, then again cold rolled with a. reduction of 30% in anotherdirection displaced approximately at a right angle the first directionof rolling to an intermediate gauge of 0.98 mm., and box-annealed for aperiod of 5 hours at a maximum holding temperature of 1100 C.

Thereafter, this' steel is further cold rolled with a reduction of 70%in the same direction as that of the second cold rolling step describedto a final gauge of 0.30 mm, and finally box-annelaed for a period of 15hours at a maximum holding temperature of 1150 C. to develop themagnetic properties thereof.

From this product, Epstein samples are taken along the final rollingdirection and also along the direction displaced at a right anglethereto, respectively, and magnetic tests are conducted on them afterthe stress relieving anneal, the results of which are as follows:

Bin Wl5/50 (gauss) (inn/kg.)

Final Rolling Direction 18, 250 0. 99 Right Angle Direction 1. 04

The above indicates an excellent cube structure.

Example 5 gitudinal direction is displaced at a right angle to thedirection of the first cold rolling. This new strip is cold rolled witha reduction of 40% to an intermediate gauge of 1.08 mm. It is thenannealed at a maximum holding tempearture of 1100 C. for a period of 10hours, then again cold rolled with a reduction of 72% in the direc- 7tion of its longitudinal length to the final gauge, then annealed at atemperature of 800 C. for a period of 3 minutes in a wet hydrogenatmosphere to decarburize it, and finally box-annealed at a maximumholding temperature of 1200 C. for a period of 20 hours in order todevelop its magnetic properties. From this product, Epstein samples aretaken along its longitudinal direction "and also along a directiondisplaced at a right angle thereto, respectively, and magnetic tests areconducted on 310 Wis/s (w-l e) Longitudinal Direction 18, 340 0.98 RightAngle Direction 18,150 1.

The above values show that a double-oriented silicon steel strip with agood cube structure has been manufactured.

We claim:

1. A process for producing double-oriented silicon steel sheet having(100) [001] crystal orientation and good magnetic properties in thefinal-rolling direction and the direction perpendicular thereto, whichcomprises (a) pickling a hot-rolled silicon steel material consistingessentially of iron, from 2.5 to 4.0% by weight Si, and from 0.010 to0.040% by weight A1, a substantial portion of said Al being inacid-soluble form which consists essentially of aluminum nitride,

([1) cold rolling said material in one direction at a reduction rate offrom about 40 to 80% (0) cross cold rolling the resulting material in adirection at an angle from 90 to an angle deviating from 90 by less than-15, with the direction of said first cold rolling and at a reductionrate of from about 30 to 70% (d) annealing the resulting cross-rolledmaterial for about one to four minutes at a temperature from 750 to 1000C. to effect decarburization and primary recrystallization, and

(e) finally annealing the material for about '5 to 40 hours at atemperature of about 900 to 1300 0,

thereby obtaining a double oriented silicon steel with (100) [001] typecrystal orientation and W 40 outstanding magnetic properties in theaforesaid two directions. 2. A process for producing double-orientedsilicon steel having (100) [001] crystal orientation and good magnetic 5properties in the final-rolling direction and the directionperpendicular thereto, which comprises (a) pickling a hot-rolled siliconsteel material consisting essentially of iron, from 2.98 to 3.11% byweight of Si, and from 0.016 to 0.030% by weight of A1, a substantialportion of said Al being in acid-soluble form which consists essentiallyof 0.0029%0.007 3% by weight, based on the hot-rolled silicon steel, ofaluminum nitride,

(b) cold rolling said material in one direction at a reduction rate offrom about to (0) cross cold rolling the resulting material in adirection at an angle from to an angle deviating from 90 by less than:15, with the direction of said first cold rolling and at a reductionrate of from about 30 to 70% (d) annealing the resulting cross-rolledmaterial at a temperature of from 750 to 1000" C. to effectdecarburization and primary recrystallization, and

(e) finally annealing the material for about 5 to 40 hours at atemperature of about 900 to 1300 0.,

thereby obtaining a double-oriented silicon steel with [001] typecrystal orientation, the magnetic induction of which, in the said twodirections and in a magnetic field of 10 oersted, exceeds 18,000 gauss.

References Cited in the file of this patent UNITED STATES PATENTS2,173,240 Wassermann Sept. 19, 1939 2,867,557 Crede Jan. 6, 19592,965,526 Wiener Dec. 20, 1960 3,008,856 Mobius Nov. 14,1961

1. A PROCESS FOR PRODUCING DOUBLE-ORIENTED SILICON STEEL SHEET HAVING(100)(001) CRYSTAL ORIENTATION AND GOOD MAGNETIC PROPERTIES IN THEFINAL-ROLLING DIRECTION AND THE DIRECTION PERPENDICULAR THERETO, WHICHCOMPRISES (A) PICKLING A HOT-ROLLED SILICON STEEL MATERIAL CONSISTINGESSENTIALLY OF IRON, FROM 2.5 TO 4.0% BY WEIGHT SI, AND FROM 0.010 TO0.040% BY WEIGHT AL, A SUBSTANTIAL PORTION OF SAID AL BEING INACID-SOLUBLE FORM WHICH CONSISTS ESSENTIALLY OF ALUMINUM NITRIDE, (B)COLD ROLLING SAID MATERIAL IN ONE DIRECTION AT A REDUCTION RATE OF FROMABOUT 40 TO 80%, (C) CROSS COLD ROLLING THE RESULTING MATERIAL IN ADIRECTION AT AN ANGLE FROM 90* TO AN ANGLE DEVIATING FROM 90* BY LESSTHAN $15*, WITH THE DIRECTION OF SAID FIRST COLD ROLLING AND AT AREDUCTION RATE OF FROM ABOUT 30 TO 70%, (D) ANNEALING THE RESULTINGCROSS-ROLLED MATERIAL FOR ABOUT ONE TO FOUR MINUTES AT A TEMPERATUREFROM 750 TO 1000*C. TO EFFECT DECARBURIZATION AND PRIMARYRECRYSTALLIZATION, AND (E) FINALLY ANNEALING THE MATERIAL FOR ABOUT 5 TO40 HOURS AT A TEMPERATURE OF ABOUT 900* TO 1300*C., THEREBY OBTAINING ADOUBLE ORIENTED SILICON STEEL WITH (100)(001) TYPE CRYSTAL ORIENTATIONAND OUTSTANDING MAGNETIC PROPERTIES IN THE AFORESAID TWO DIRECTIONS.